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STP12 Abstracts Berlin, 12 - 16 July 2010 SCOSTEP Symposium 2010 Transient climate simulations from the Maunder Minimum to present day including a detailed stratosphere Spangehl Thomas 1 , Cubasch Ulrich 1 , Raible Christoph C. 2 , Schimanke Semjon 1 , Körper Janina 1 , Hofer Dominik 2 1 Institut für Meteorologie, Freie Universität Berlin, 2 Climate and Environmental Physics, Physics Institute, University of Bern; Oeschger Centre for Climate Change Research Transient climate simulations are performed covering the period from 1630 to 2000. A vertically extended version of a coupled atmosphere-ocean general circulation model is used, including a detailed representation of the stratosphere. One simulation is driven by changes in total solar irradiance due to solar activity as well as volcanic eruptions and changes in greenhouse gas (GHG) concentrations. A second simulation additionally includes changes in short-wave heating due to prescribed photochemical changes in ozone. A third simulation includes higher resolved changes in the UV/visible part of the solar spectrum combined with lower changes in TSI. The simulations are compared with reconstructions and other simulations employing less resolved stratosphere. The inclusion of the higher resolved stratosphere does only play a moderate role for the simulated climate variability on the hemispheric scale. By contrast the use of lower TSI changes combined with the higher resolved changes in short wave fluxes results in a clear reduction of changes in annual NH mean near surface temperature. All three simulations reveal a shift of the North Atlantic Oscillation toward a more positive phase from the Maunder Minimum to present day, mainly attributed to the anthropogenic increase in concentration of well-mixed GHG. The increase in GHG is related to a more disturbed stratospheric polar vortex resulting in an only moderate strengthening of tropospheric westerlies over Europe compared with the tropospheric version of the model. On multidecadal to centennial time scales the stratospheric solar forcing substantially contributes to the climate change signal in the stratosphere, and there is clear evidence for an impact on the tropospheric circulation.
STP12 Abstracts Berlin, 12 - 16 July 2010 SCOSTEP Symposium 2010 A partial review of current progress with our understanding of small scale ionospheric irregularities and of some of the remaining challenges. St-Maurice Jean-Pierre ISAS, University of Saskatchewan The advent of increasingly high temporal and spatial resolution instruments coupled with a growing global perspective on the subject has meant that even some very basic properties of ionospheric irregularities have continued to challenge our understanding, this in spite of impressive progress in our capability to perform sophisticated numerical simulations. A brief presentation on the subject can only cover a limited range of topics. Here we will only look at some of the challenges associated with short scale irregularities accessible to ground-based radars. Even then, there is a long list of questions to choose from such as: the age-old question of what causes the saturation of E region irregularities at something comparable to the ion-acoustic speed of the medium; how aspect angles have to grow as individual structures evolve and how these same aspect angles relate to saturation and to electron heating at high latitudes; the possible role played by anomalous diffusion; the possible origin of very low altitude E region echoes; the possible origin of up-down and east-west asymmetries seen in E region echoes below 105 km at low latitudes; the non-local character of gradient-drift irregularities higher up; what we know we don't know about so-called 150 km echoes; `wall echoes' in the lower F region at mid-latitudes; the origin of the systematic lower Doppler shifts seen by HF radars in comparison to drifts determined from other techniques; the question of what seeds equatorial spread F and the possible connection with the pre-reversal enhancement in the low latitude electric field.
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scostep 2010 (stp12) - Leibniz-Institut für Atmosphärenphysik an der ...

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